1. Field of the Invention
The invention relates to a method of manufacturing a liquid crystal display panel. In particular, the invention relates to a method of manufacture whereby the steps of forming a plurality of micro-cell structures on one substrate of the display, injecting the liquid crystal into the cells and sealing the two substrates accomplish the manufacture of the liquid crystal display.
2. Description of the Related Art
FIG. 1 shows a basic structure of the conventional liquid crystal panel. As shown in FIG. 1, a thin layer of liquid crystal 2 is retained between two substrates 16a, 16b by a sealing member 19. The substrate 16a has transparent electrodes 17a formed on regions of the inner surface thereof, with an alignment layer 18a (i.e. for molecular alignment of the liquid crystal) formed over the electrodes and the remainder of the inner surface of the substrate. The substrate 16b is similarly formed with transparent electrodes 17b and alignment layer 18b. Spacers 23 are disposed in the liquid crystal, for maintaining a uniform size of gap between the two opposing surfaces of the substrates.
In general, it is necessary to mutually laterally position the two substrates of a liquid crystal display panel to a very high degree of accuracy, i.e. to position one substrate very precisely above the other. The most popular method of manufacture for such a liquid crystal display panel is as follows. Firstly, an empty cavity is formed, i.e. consisting of the two opposed substrates 16a, 16b accurately mutually aligned, and mutually attached by the sealing member 19 between them, but without the liquid crystal 2. The cavity is then filled with the liquid crystal 2, utilizing a vacuum insertion method, and then sealed. However such a method has various disadvantages, such as a considerable length of time being required to complete the process of filling the cavity with the liquid crystal 2, in the case of a large-size liquid crystal display panel.
For that reason, a method of manufacture has been proposed which is based upon first dropping liquid crystal onto a substrate, as described in Japanese Patent Laid-open No. 62-89025. The basic concepts of the “dropping” method are illustrated in FIG. 2, in which a sealing member 22 is formed in a peripheral region of one substrate 20a, while liquid crystal 21 is dropped onto the other substrate 20b. With the two substrates held spaced apart, the substrates are placed within a vacuum chamber of a vacuum assembly apparatus. In that condition (still under atmospheric pressure), the lateral positions of the two substrates 20a, 20b are mutually aligned, i.e. so that the substrate 20a becomes positioned precisely above the substrate 20b. The air pressure within the vacuum chamber is then reduced, and under the condition of the low pressure, the two substrates are brought together so that the substrate 20a becomes superposed on the substrate 20b. Thereafter, the sealing member 22 is hardened, e.g. by application of suitable radiation.
However, with this method, it is necessary to execute very accurate mutual lateral alignment of the two substrates while the substrates are within the vacuum chamber, with the substrates being held apart by only a few millimeters. It is therefore necessary to achieve a positioning accuracy within the range of several microns to several tens of microns, for position adjustment and position control within the vacuum chamber. Hence, the overall size, complexity and cost of a vacuum assembly apparatus that utilizes such a vacuum chamber are excessive. Moreover, this will result in an increase in the most common causes of defects in liquid crystal display panels, i.e. defects due to the presence of dust particles within the panel cavity, short-circuits between the electrodes of the upper and lower substrate, etc.